If making your own dulce de leche, the day before baking remove the paper wrapping on the cans of sweetened condensed milk and place the cans sideways in a large pot. Fill the pot with water until at least 1 inch above the cans. Bring the water to a boil and lower to a simmer, cooking them for 3 hours. Put an alarm on every 30 minutes and check the water level and add water to top off as needed. NEVER let the water level fall below the can level as the cans could explode. After 3 hours, gently remove the cans from the water and leave the can to cool 100% completely (overnight best). Opening them before could again result in an explosion.

Mix the cornstarch, all purpose flour, baking soda, baking powder, and salt in a bowl. Set aside.

In a mixing bowl, beat the icing sugar and butter together. Add in an egg yolk at a time, beating well after each addition. Finally, mix in the vanilla extract and orange zest.

Add 1/3 of the flour mixture and mix until just combined. Repeat the process for another 1/3 of the flour mixture. Place remaining 1/3 of the flour mixture on the counter and place the dough on top. Gently fold the mixture onto itself and gently press the dough with your palm. Continue until the dough has absorbed the remaining flour. The less you handle the dough the softer to cookies will be. Wrap the dough with cling film and chill for 30 minutes in the fridge.

Preheat oven to 180 C (360 F). Take 1/2 the dough and place the other half back in the fridge. Roll out the dough to a thickness of 8-10 mm. Cut out circles using a 4.5 cm or 6 cm diameter cookie cutter. Place the circles on a greased and floured baking tray. Place the baking tray in the fridge and repeat with the 2nd batch on a 2nd tray. The smaller cookie cutter will give you 24 cookies (48 circles) and the bigger cookie cutter will give you 18 cookies (36 circles).

Bake for 10-12 minutes or until cooked but the cookies should not become golden. Cool in a rack.

Alfajores assembly: with the bottom facing uptake, spoon a good amount of dulce de leche on it and spread it with a knife right up to the edge. The dulce de leche should be the same height as the cookie. Top with another cookie like a sandwich lightly press. Run a clean finger around to smooth out the filling. Roll he sides of the cookies coconut flakes to cover the dulce de leche. Repeat until all the cookies are done.